linux-kernel - [PATCH bpf-next v1] bpftool: Add support for querying cgroup

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Date:   Mon, 29 Aug 2022 16:18:28 -0700
From:   Hao Luo <haoluo@...gle.com>
To:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Quentin Monnet <quentin@...valent.com>,
        Hao Luo <haoluo@...gle.com>
Subject: [PATCH bpf-next v1] bpftool: Add support for querying cgroup_iter link

Support dumping info of a cgroup_iter link. This includes
showing the cgroup's id and the order for walking the cgroup
hierarchy. Example output is as follows:

> bpftool link show
1: iter  prog 2  target_name bpf_map
2: iter  prog 3  target_name bpf_prog
3: iter  prog 12  target_name cgroup  cgroup_id 72  order self_only

> bpftool -p link show
[{
        "id": 1,
        "type": "iter",
        "prog_id": 2,
        "target_name": "bpf_map"
    },{
        "id": 2,
        "type": "iter",
        "prog_id": 3,
        "target_name": "bpf_prog"
    },{
        "id": 3,
        "type": "iter",
        "prog_id": 12,
        "target_name": "cgroup",
        "cgroup_id": 72,
        "order": "self_only"
    }
]

Signed-off-by: Hao Luo <haoluo@...gle.com>
---
 tools/bpf/bpftool/link.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 7a20931c3250..9e8d14d0114d 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -83,6 +83,29 @@ static bool is_iter_map_target(const char *target_name)
 	       strcmp(target_name, "bpf_sk_storage_map") == 0;
 }
 
+static bool is_iter_cgroup_target(const char *target_name)
+{
+	return strcmp(target_name, "cgroup") == 0;
+}
+
+static const char *cgroup_order_string(__u32 order)
+{
+	switch (order) {
+	case BPF_CGROUP_ITER_ORDER_UNSPEC:
+		return "order_unspec";
+	case BPF_CGROUP_ITER_SELF_ONLY:
+		return "self_only";
+	case BPF_CGROUP_ITER_DESCENDANTS_PRE:
+		return "descendants_pre";
+	case BPF_CGROUP_ITER_DESCENDANTS_POST:
+		return "descendants_post";
+	case BPF_CGROUP_ITER_ANCESTORS_UP:
+		return "ancestors_up";
+	default: /* won't happen */
+		return "";
+	}
+}
+
 static void show_iter_json(struct bpf_link_info *info, json_writer_t *wtr)
 {
 	const char *target_name = u64_to_ptr(info->iter.target_name);
@@ -91,6 +114,12 @@ static void show_iter_json(struct bpf_link_info *info, json_writer_t *wtr)
 
 	if (is_iter_map_target(target_name))
 		jsonw_uint_field(wtr, "map_id", info->iter.map.map_id);
+
+	if (is_iter_cgroup_target(target_name)) {
+		jsonw_lluint_field(wtr, "cgroup_id", info->iter.cgroup.cgroup_id);
+		jsonw_string_field(wtr, "order",
+				   cgroup_order_string(info->iter.cgroup.order));
+	}
 }
 
 static int get_prog_info(int prog_id, struct bpf_prog_info *info)
@@ -208,6 +237,12 @@ static void show_iter_plain(struct bpf_link_info *info)
 
 	if (is_iter_map_target(target_name))
 		printf("map_id %u  ", info->iter.map.map_id);
+
+	if (is_iter_cgroup_target(target_name)) {
+		printf("cgroup_id %llu  ", info->iter.cgroup.cgroup_id);
+		printf("order %s  ",
+		       cgroup_order_string(info->iter.cgroup.order));
+	}
 }
 
 static int show_link_close_plain(int fd, struct bpf_link_info *info)
-- 
2.37.2.672.g94769d06f0-goog